With the progress and development of science and technology, a liquid crystal display is widely applied to various information display devices because of aspects such as a thin and light design and low power consumption. In various applications, the liquid crystal display may be divided into a direct-viewing-type pattern, for example, when the liquid crystal display is applied to a mobile phone or a tablet computer, a user can directly view image information displayed on the liquid crystal display, and a projection-type pattern, for example, when the liquid crystal display is applied to a vehicle head up display (head up display, HUD), driving image information displayed on the liquid crystal display is displayed on a windshield of an automobile projectively.
In the head up display of the projection-type pattern, the head up display mostly uses a thin film transistor liquid crystal display as an image source, and guides a light path by using an optical system design so that the light path is imaged on the windshield. Generally, to acquire a clear projection image on the windshield, the liquid crystal display of the head up display generally needs high backlight luminance to withstand effects of ambient light. Therefore, later people add a white sub-pixel (W) into a conventional RGB liquid crystal display (the liquid crystal display may be called an RGBW liquid crystal display later), so that a needed backlight luminance is reduced by improving the penetration rate of the liquid crystal display.
However, although the design of the RGBW liquid crystal display into which the white sub-pixel (W) is added can greatly improve the penetration rate, the areas of pure-color (that is, red, green, and blue) sub-pixels are reduced, consequently, the pure-color luminance becomes lower, and the white luminance is too high, further leading to the deteriorated image quality.